Safety device for electric cooking and heating devices



Sept. 30 1924. "i 1,510,409

H. -MAN/BAUM Y Y l SAFETY DEVICE FOR ELECTRIC COOKING AND HEATINGDEVICES Filed March 29, 1922 Patented Sept. 30, 1924.

PATENT OFFICE.

HEINRICH IAYBAUI, F SUNDERN, GEBIANY.

SAFETY DEVICE FOB. ELECTRIC COOKING AND HEATING DEVICES.

Application med Iarch 89, 1922. Serial No. 547,916.

To all whom 'it may concern:

Be it known that I, HEINRICH MAYBAUM, residing at Sundern, District ofArnsberg, Germany, have invented certain new and useful Im rovements inSafety Devices for Electric boking and Heati Devices, of which thefollowing is a speci cation.

It is known, that electrical boilers, cooking devices and the like areliable to be seriously damaged and put out of service when beingoverheated, for example when being, byneglect, left in the electrlccircuit in a liquid-empty state. Special safety devices have thereforebeen proposed which automatically interrupt or break the circuit, assoon as the temperature passes beyond its admissible u perlimit. Thesesafety devices norma y com rise a socalled `fuse member consisting o ametal of low melting point, for example an alloy of lead,tin

and bismuth which, whenever the temperature increases to, al dangerousdegree, becomes softened and fuses away, so that the circuit is eitherdirectly interrupted or a circuit closin device controlled by the fusemember eased and permitted to breakthe circuit. 1

It is the p ose of this invention to improve these sa ety devices by soarranging the fuse member, that the same is severed by vcombined fusingand mechanical action. As a matter of fact it may happen, that the usercuts out the Ielectrical current, when the fuse member has just begun tosoften 85 and is just in a condi-tion of plastic or elastic deformationin which it remains, when the apaparatus is permitted to cool down tononm temperature. In this state Athe circuit closing contacts controlledby the fuse mem- 0 ber may however be in a partly opened condition, sothat u n further use sparking occurs between t em, whereb the a paratusmay again be seriously amage or disabled. My invention thereforeprovides meanswhereby the fuse member is positively severed by combinedheat and mechanical action, whenever it begins to soften by an undueincrease of temperature. It

starts from the fact, that most'of the alloys 5 of low meltin point are,while being in a cold state, o a comparatively great 4mechanicalstrength, which however rapidly deL creases, as soon as the metal beginsto soften under the influence of heat.

According to the main feature of my invention I therefore provide asafety device of the kind described in which the fuse member forms thesupport of the central guiding pin of a movable contact carrying memberwhereby the same can be held in its current closing position. Thiscentral guiding pin is guided in the central bore of a stationary sleevehavin also a lateral bore in which a fuse pin is located so as to beacted upon intermediate its ends by the end of the guiding pin. As soonas the fuse pin begins. to soften its mechanical strengthrapidly"decreases, so that the centrallguiding pin may under theinfluence of its circuit opening spring which tends to move the contact.carrying member-l into its circuit breaking position, act as a kind ofshearing punch and break or shear out instantaneously and Without failthe central portion of the fuse pin which formerly held the movablecontact member against the action of its spring. This means then, that,whenever the fuse pin begins to soften, it is positively severed by thecombined action of heating and mechanical means and with a snap action,so that the circuit closing contact is fully opened and sparkingprevented. Another feature of my invention resides in the arrangement ofan additional spring between the movable contact carry'in member and theproper contact secur to it whereby the contact closure may be `preservedand spanking avoided .during the fraction of time during which breakingof the fuse pin occurs, as will be more fully described in detailhereafter.

My invention is besides in its preferred embodiment illustrated in theaccompanying drawings in which:

Fi 1 is a vertical section of an electri cooking pot provided with thenew safety device, the same being shown in its circu1t closing position,l

Fig. 2 a part of the same section, the safety device being shown in itsfcircuit breaking position,

Fig. 3 a plan-view of Fig. 2.

lated therefrom by a mica plate 1t.

In the drawing a desi ates an electrical cooking or'- boiling vesse orheating device ot any known or suitable construction, the lowercontracted portion b of which is surrounded by the resistance or heatingunit c. The lower portion of the vessel a is enclosed within acylindrical base d the the mantle of which practically forms thecontinuation of the uncontracted part of the mantle a. '.lhe members aand d are detachably secured to each other in any known or suitable way,for example by a screw and nut connection e, f.

g', It designate the usual contact pins; and while I have shown. in thedrawings only two ot those Contact pins, it is obvious, that other pinsmay be added if the apparatus is to be operated with different currenttensions. This is well known in the art and needs no further:description. 0f the two contact pins pin g is by a piece of copper z'"connected with a movable contact m controlled by the fuse pin, as willbe hereafter described more in detail, whereas contact pin b isconnected to the one end of the resistance wire of the heating unit c bymeans of a piece of wire Z which is insulated by glass beads 7c.

The contact member m is secured to a cup shaped contact carrying memberp by means of a compression spring o and inslili- 'I e member p is underthe influence of a helical spring 1', which tends to move it into itscircuit breaking position as illustrated in Fi 2 of the drawing. The cup1s guide by a stationary sleeve s which is permanently attached to thebottom portion t of the base member d and into which a sleeve u isdetachably screwed. This detachable sleeve u is provided with a centralvertical bore or recess formin a guide for the central guiding pin g oft e cup p and is at its upper end provided with a transverse passageadaptedto receive a fuse pin o.

When the apparatus is to be used and is in its cold state, a fuse pin ois inserted into the transverse bore of the screw plug u and the samescrewed into the sleeve s Immediately the section of the fuse pincrossing the central bore of the plug u engages the lower end of theguide pin g, so that upon furtherentrance ofthe plug u the cup p islifted into its circuit'closing position according to Fig. 1 and againstthe tension of spring 1'.

In this circuit closing position the contact plate m is in contact withthe contact plate a: secured to the bottom plate fw .of the bowl a: andduly insulated therefrom, whereb the circuit is closed, and theintermedlate sprin oy is in its compressed condition. In this circuitclosing position as is well known with this kind of safety devices. Inbecoming soft its mechanical strength rapidly decreases so that thecentral guiding pin g may now act as some kind of a punch andinstantaneously and without fail sever the fuse pin intermedi'- ate itsends which are carried by thetransverse bore of the screw plug u. Thespring 1' is by this severing of the fuse pin re-.4

leasedl and adapted to break the contact with` a snap like action. andwithout any sparking. During the little interval of time which passesbetween the beginning of the softening of the fuse pin and its being`severed by the combined heat and punching action the spring o becomesgradually released and holds the contact members m, 4v in their circuitclosin position until the spring 1' is completely re eased and the rapiddown stroke of the cu p may occur, which snaps the'contact memlber maway from the contact member o The current is thus broken, so that anydamage of the apparatus by overheating is safely prevented. In order toreadjust the apparatus for further use after a cutting out of thecurrent one screws out the plug u and inserts a fuse pin into thetransverse bore, `whereupon the plug u may be reinserted and theapparatus is ready for further use.

While I have in the -oregoin specification and in the drawing describeand illustrated my invention in its application to particular electricalheating device and in an embodiment in which the fuse pin does not formitself part of the circuit, it is obvious to those skilled in the artthatmy invention may just as well be used with any other kind of cookingand heating apparatus, caloric and thermic devices and the like in whichthe so-called dry burning is to bev avoided and over heating of thedevice beyond a certain temperature positively prevented or in which thefuse pin forms itself part of the circuit.

What I claim as my invention isz- A safety circuit breaker comprising astationary guide sleeve carrying a "fuse pin, a contact carrying memberguided by said guide sleeve and movable into circuit making and circuitbreaking positions; a spring biasing said contact carrying member to itscontact breaking position, a circuit contact carried by said contactcarryin member, .a compressible spring interposed tween said circuitcontact and said contact carrying pin and thereby break the circuit whenthe 10 member and compressed therebetween when fuse pin becomesrelatively hot.

the contact carrying member is in its cir- In testimon whereof I aix mysignature cuit making position, and a guiding pin. on in presence o twowitnesses.

said contact carrying member for engaging the fuse pin whereby to holdthe contact HEINRICH MAYBAUM carrying member in its circuit makin posi-Witnesses: tion when the fuse pin is relatively co d, the WILHELMINEHEIMANN,

rst said spring operating to break the fuse ELISABETH Fmsnmn.

